Refrigerating apparatus with defrost control means



March 23, 1965 A. J. KUHN ETAL REFRIGERATING APPARATUS WITH DEFRO ST CONTROL MEANS Filed Dec. 24, 1962 2 Sheets-Sheet 1 Fig. 2

, INVENTORS Albert J Ku/m BY Leonard J. Mann D The/r Attorney March 23, 1965 REFRIGERATING APPARATUS WITH DEFROST CONTROL MEANS Filed D80- 24, 1962 2 Sheets-Sheet 2 M 337 I40 1 V 2647 215s use 323 Fig. 6

INVENTORS Albert J. Ku/m BY Leanard J. Mann Their A/Iomey United States Patent 3 174,297 REFRlGERATlNG AP PARATUS WITH DEFRQST CGNTROL MEANS Albert J. Kuhn and Leonard 3. Mann, Dayton, Ohio,

assignors to General Motors (Iorporation, Detroit,

Mich, a corporation of Delaware Filed Dec. 24, 1962, Ser. No. 246,734 6 Claims. (Cl. 62156) This invention pertains to refrigerating apparatus and more particularly to control systems for two-compartment refrigerators, especially those cooled by a single refrigerating system.

Two-compartment refrigerators normally provide more satisfactory refrigerating temperatures in each compartment. Since the control of refrigerating systems is usually responsive to the temperature of only one of the compartments, there may be circumstances under which the other compartment is not adequately refrigerated. This is more likely to occur when the refrigerating system is made as simple as possible, for example, where only one evaporator is used to cool both compartments and where the air from both compartments is circulated over the single evaporator.

It is an object of this invention to provide a control system for the control of refrigerating temperatures in both compartments which will provide increased refrigeration for one of the compartments in response to unusual demand during unusually low ambient temperatures.

It is another object of this invention to provide a control system for a single evaporator two-compartment refrigerator in which, during the operating periods of the refrigerating system, the air is circulated by fan between the evaporator and both compartments characterized by an additional control for operating the fan whenever the temperature of the higher temperature compartment is not maintained even though the refrigerating system may have been idle.

t is another object of this invention to provide a control system for a single evaporator, two-compartment refrigerator in which, during operating periods of the refrigerating system, the air is circulated by a fan beween the evaporator and the compartments and throttled to one of the compartments by a thermostatic air valve to keep its temperature above freezing characterized by an additional control responsive to a predetermined opening of the air valve for operating said fan even though the refrigerating system may have been idle.

These and other objects are attained in the form shown in the drawings in which a two-compartment refrigerator is provided with a single finned evaporator beneath the false bottom wall of the below-freezing compartment. Air is drawn from both compartments through the evaporator by a dual outlet fan which discharges most of the air directly into the below-freezing compartment and the remainder of the air under a control of a thermostatic throttling valve back into the above-freezing compartment. The refrigerating system and the fan are simultaneously started and stopped in accordance with predetermined high and low temperatures of the belowfreezing compartment. According to one form of my invention, when the thermostatic valve is wide open in response to a high temperature of the above-freezing compartment, a double throw switch disconnects the fan motor from control of the thermostatic switch and closes a shunt to cause the operation of the fan motor to provide additional cooling of the above-freezing compartment to prevent an abnormal temperature rise during the idle period of the refrigerating system.

In another form of the invention, when the valve is in a wide open position, it causes the starting of both the fan motor and the compressor motor to prevent the above-freezing compartment from rising above the desired temperature. This is accomplished through either a double-throw switch arrangement or by energizing a biasing heater upon the thermostat bulb of the main refrigeration switch which is responsive otherwise to the temperature of the below-freezing compartment. Defrosting may either be obtained through the use of a timer motor operating a double-throw switch or through the use of a defrost control thermostat upon the evaporator which is provided with a defrost delaying element heater deenergized in the wide open position of the valve. In the last form, if the evaporator is sufiiciently covered with frost, a defrosting cycle will take place.

Further objects and advantages. of the present invention will be apparent from the. following description, reference being had to the accompanying drawings wherein several preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a vertical, side sectional View of a twocompartment single evaporator refrigerator embodying one form of my invention;

FIGURE 2 is a wiring diagram for the refrigerator shown in- FIGURE 1 embodying one form of my invention;

FEGURE 3 is a second wiring diagram for the refrigerator shown in FIGURE 1 showing another form of my invention;

FlGURE 4 is a third wiring diagram for the refrigerator shown in FIGURE 1 illustrating a third form of the invention;

FIGURE 5 is a fourth wiring diagram for the refrig erator shown in FIGURE 1 illustrating a fourth form of the invention; and

FIGURE 6 is a fifth wiring diagram for the refrigerator shown in FEGURE 1 illustrating a fifth form of the invention.

Referring now more particularly to FIGURE 1, there is shown an insulated refrigerator cabinet 29 having an upper below-freezing compartment 22 surrounded by insulated walls and provided with a separate insulated door 24 and a lower above-freezing compartment 26 likewise surrounded by insulated walls and provided with a separate insulated front door 28. At the top of the above-freezing compartment 26, there is provided an insulated horizontal dividing wall 30 provided with an air passage 32 which extends up into a rear corner of an evaporator compartment 34 above it. This evaporator compartment 34 is provided by the false bottom sheet metal wall 36 at the bottom of the below-freezing compartment 22 which rests upon the vertically finned refrigerant evaporator 38 having transverse fins extending from front. to rear provided upon the horizontal serpentine refrigerant coils it).

The evaporator compartment 34- and the evaporator 38 are divided from front to rear by a partition wall which controls the flow of air from the passage 32 so that it will move forwardly to the front of the compartment 34 where the forward flowing air mixes with air flowing from the below-freezing compartment in through openings 32 at the front of the compartment 34. Fromthat area the mixed air flows rearwardly between the fins of the remaining portion of the evaporator 38 to the inlet shroud 44 of the double outlet centrifugal fan 46 driven by tne electric motor 43. The fan 46 has an upwardly extending outlet 59 which discharges the air freelyinto the below-freezing compartment 22. This fan 45 also has a downwardly extending discharge outlet 5?. leading to an insulated passage 54 in theinsulated rear wall 56' of the refrigerator 20. The passage 54 Patented Mar. 23, 1965 3 connects with the inlet of the air valve 58 likewise located in the insulated rear wall 56 which discharges through the outlet 68 into the above-freezing compartment 28. The valve 58 includes a valve element 62 connected by a valve stem 64 with a fluid motor 66 likewise located in the insulated rear wall 56. The fluid motor 66 is connected by a capillary tube 68 to a thermostat bulb 7t) fastened to the inner face of the rear wall 56 where it is exposed to the temperature of the air within the abovefreezing compartment 26.

The valve stem 64 carries a projection 72 which is adapted when the valve element 62 is in the fully open position to engage and depress the plunger '74 of the switch 76 likewise located in the insulated rear wall 56. The fluid motor 66, by reason of being located in the insulated rear wall 56, is maintained at a higher temperature than the above-freezing compartment 26 and the bulb 79 so as to isure that the valve element 62 will be controlled in accordance with the temperature of the above-freezing compartment 26. The refrigerator is also provided with a defrost control switch 78 located on the rear portion of the evaporator 38 so that it is responsive primarily to the temperature of the evaporator 33 and also is subjected to the temperature of the above-freezing compartment air flowing to the evaporator 33 from the passage 32. It is in the partitioned portion of the evaporator 38 through which flows forwardly the above-freezing compartment air from the passage 32.

Referring now more particularly to FIGURE 2, there is illustrated one form of control system embodying my invention. This wiring diagram includes the supply conductors 121 and 123. The supply conductor 123 connects through a compressor motor 125 and the conductors 127 and 129 with a snap-acting thermostat switch 131 which, in turn, connects and disconnects the conductor 129 from the conductor 132. The conductor 132 normally connects through the double-throw defrost switch 134 with the supply conductor 121. The supply conductor 123 is also connected to one terminal of the fan motor 48. The second terminal of the fan motor 48 is connected to the double-throw switch member 136 of the switch 76 which, under normal temperatures in the above-freezing compartment, is normally in engagement with the lowercontact connecting to the conductor 129. By this arrangement, the fan motor 48, as well as the compressor motor 125, are started and stopped simultaneously by the closing and opening of the thermostatic snap-acting switch 131. This thermostatic snap-acting switch 131 is connected through a capillary tube 139 to a thermosensitive element 14% which is in heat transfer relation with the liner of the below-freezing compartment 22 directly above the upper outlet 50 of the fan 46 so that it is substantially responsive to the temperature of the below-freezing compartment 22. Preferably this switch 131 is set to close when the compartment 22 reaches a temperature of about +11 F. and to open when the compartment 22 reaches a temperature 2 F.

The switch 76 is preferably of the close differential snap-action type. It is arranged to be operated by a projection 72 when the temperature of the bulb 70 and the compartment 26 reaches a temperature of 40 F. When this is reached, the plunger 74 is depressed so as to move the switch member 136 out of contact with its lower contact 138 and into contact with its upper contact,

144 which connects with the conductor 146 extending in shunt circuit arrangement to the thermostatic switch 131 and connects with the conductor 132. This takes the fan motor 48 away from the control of the snap-acting thermostat switch 131 and connects it directly to the switch 134 so that it will operate continuously excepting during a defrost period. The fan motor 48 will remain so connected until the above-freezing compartment 26 and the thermostat bulb 70 will be cooled to a temperature of about 38 F. at which the valve element 62 will throttle the air being delivered to the above-freezing compartment and will cause the projection 72 to move away from the plunger 74 sufliciently to cause the biased switch 76 to move its double throw contact 136 out of contact with its upper contact 144 back into contact with its lower contact 138 to reconnect the fan motor 48 in parallel circuit with the compressor motor under the control of the snap-acting thermostatic switch 131.

To maintain the temperature of the below-freezing compartment 22 between +ll and 2 R, the evaporator 38 must be operated at even lower temperatures so that it will gradually collect frost from the air being circulated through it and the evaporator compartment 34. As shown in FIGURE 2, there is provided a timer motor 148 which is connected across the supply conductors 121 and 123. At periodical intervals such as once or twice a day, the timer motor 148 through the operating mechanism 158 will operate the defrost control switch 134 from its lower contact 151 into contact with its upper contact 152. The contact 152 connects through the conductor 154to the snap-acting bimetal contact member 156 of the switch 78 which is mounted upon the evaporator 38 as previously described. This switch 156 connects through the conductor 158 to the defrost heater 160 which is mounted in slots in the upper and lower edges of the fins of the evaporator 38 as shown in FIGURE 1. This heating of the evaporator 38 quickly defrosts it. When the evaporator 33 is defrosted, the rise in temperature will cause the snap-acting bimetal 156 to snap to the open position to deenergize the heater 160. While the defrost switch 134 is in contact with the contact 152, both the compressor motor 125 and the fan motor 48 will be de energized. After the expiration of a sufiicient time to defrost the evaporator 38, the timer motor 148 through the mechanism 150 will return the contact 134 to its lower position wherein it connects through the contact 151 directly with the conductors 132 and 146 for resuming normal refrigeration.

In the form shown in FIGURE 3, the defrost system is identical to that shown in FIGURE 2 and bears the same reference characters. It is similarly connected to the supply conductors 173 and 172. The fan motor 48 and the compression motor 125 each have their second terminals connected to the supply conductor 172. Their first terminals are connected respectively by the conductors 174 and 176 through a common conductor 178 to one terminal of the snap-acting thermostatic switch 131 which connects to the lower contact 180 of the defrost switch 134.

According to our invention, an arrangement is provided whereby upon a sufficiently wide opening of the valve 58, both the fan motor 48 and the compressor motor 125 are caused to operate. This takes place even though the compartment 22 is at a sufficiently low temperature, such as 0 F. to 5 F., for example. This supplementary operation is accomplished by making the contact member 182 within the switch 76 of the normally open type and arranging the projection 72 and the plunger 74 so that the contact member 182 closes when the compartment 26 and the bulb 7 0 reaches a temperature of 40 F.

When this is done, the conductor 184 connecting with the lower contact 80 connects through the switch 182 and the conductor 186 to a low-wattage electric heater 188 which is located in heat transfer relation with the bulb 140. The second terminal of this heater 188 connects through the conductor 199 with the supply conductor 172. Therefore, when the compartment 26 and the bulb 70 reach a temperature of 40 F., the switch 182 closes to energize the heater 188 to heat the bulb 146 so as to cause the switch 131 to close in order to energize the fan motor 48 and the compressor 125. This will cause cold air to be discharged into the compartment 26 to lower its temperature. When the compartment 26 has been cooled to about 38 F., the switch 182 will open to deenergize the heater 188 to place the control of the system again in response to the temperature of the below-freezing compartment 22. This arrangement likewise provides for added cooling of the compartment 22 whenits temperature reaches 40 F.

In the form shown in FIGURE 4, the second supply conductor 222 connects to the second terminal of the fan motor 48 and the compressor motor 125. The compressor motor 125 and the fan motor 48 have their first terminals connected respectively by the conductors 224 and 226 to a conductor 228 connecting with one terminal of the thermostatic switch 131. The second terminal of the snap-acting thermostatic switch 13} connects through the conductor 23%) with the upper termina 232 of the thermostatic switch 78. The thermostatic switch 78 includes a double-throw snap-acting bimetal switch 234 which is adapted to snap from its position in engagement with the upper contact 232 into engagement with it lower contact 236 when it reaches a temperature of 28 F. When the temperature of the switch 73 and the bimetal 23 iis raised to a temperature of 55 B, it will snap from its position in contact with the lower contact 236 upwardly into contact with its upper contact 232.

To prevent the snap-acting thermostatic switch 234 mm being moved away from is upper position when no defrosting is required, we provide a small four-watt electric heater 23-8 in heat transfer relation with the casing of the switch 78 which includes the snap-acting bimetal switch 234 as shown in FIGURE 4. To energize this heater 23%, there is a conductor 2% connecting the upper contact 232 with the double-throw element 242 of the switch 76 which is operated by the plunger 74. in the normal position of the valve 58, the double-throw switch element 242. is normally in contact with the lower contact 2 .4 to supply electric energy through the resistor 246 and the conductor 243 with one terminal of the defrost control heater 238. The other terminal of the heater 238 is connected through the conductor 25%? to the supply conductor 222. Connected in shunt with the heater 238 is a second resistor 252 and a thermistor 254 which is a negative temperature responsive resistance which prefen ably is located beneath the cover 25-5 on the outside of the rear wall 56 of the cabinet so that it is responsive to ambient temperature. The arrangement of the resistors 245 and 252 as well as the thermistor 254 provided with suitable values constitute a form of voltage compensation for the heater 238 so that it is substantially una fected by voltage variations of the supply conductors 229 and 222.

Under certain conditions, the above-freezing compartment may rise abnormally above its normal refrigerating storage temperature maintained and controlled by the value 53. This may be the result or" placing a large food load in the above-freezing compartment 26 or allowing the door 28 to remain open for a longer than normal period or it may be due to excessively high environment temperatures. This may also be caused by an excessive collection of frost upon the evaporator 38. Whether the high temperature results from any of these causes, the high temperature will be reflected in the pressure within the bulb 7t} and the fluid motor 65 thereby causing the valve element 62 to be moved open wide so that the projection 72 will engage the plunger 74 and snap the double-throw switch element 242 away from its lower contact 244 and its lower position shown in FIGURE 4 to its upper position where it engages the upper contact 253. This upper contact 258 connects to the conductors 269 and 225 to cause energization of the fan motor 48 and the compressor motor 125 as long as the snap-acting bimetal switch 23 remains in engagement with the upper contact 232.

The movement of the double-throw switch contact 242 away from the lower contact 244 will decnergize the defront control heater 23% thereby allowing the container of the switch 78 and the snap-acting bimetal switch 234 to be further cooled by the evaporator 33. During this period the fan motor 48 and the compressor motor 125 will operate to provide additional cooling for the compartment 2e. If this cooling is sufiicient, it may allow the thermostat bulb 7th to be cooled sufiiciently to cause the fluid motor 66 to allow the valve 58 to throttle andalso to move the projection 72 away from the plunger 74 thereby allowing the switch 242 to return to its lower position. However, if the heat load of the compartment 26 remains high or if the evaporator 38 is considerably frosted, the temperature within the compartment 26 will remain high and the heater 238 will therefore remain deenergized.

The snap-acting bimetal 234 will then be cooled below its tripping point of 28 F. causing it to be snapped away from the upper contact 232 into engagement with its lower contact 236 to deenerglze the motor 48 and as well as the circuit of the heater 233 and the resistors 246 and 252 as well as the thermistor 254. The engagement of the contact 236 will, through the conductor 262 and the normally closed thermostatic bimetal switch 264 and the conductor 266, energize the defrost heater to melt the frost from the evaporator 38. This will continue until the evaporator 33 is heated enough to completely defrost it and its temperature rises to the return tripping point of the snap-acting bimetal switch 234 which has been selected as 55 F.

When this occurs, the switch 234 will snap away from its lower contact 236 and back into contact with its upper contact 232 causing the restarting of a refrigerating system. The snap-acting switch 131 will normally be in the closed position because ofthe absence of refrigeration during the defrost period so that the fan motor 43 and the compressor motor 125 will be energized through this switch. However, the fan motor 48 and the compressor motor 125 will be energized through this switch. However, the fan motor 43 and the compressor motor 125 will also be energized through the switch 242 as long as the air valve 55; remains in the wide-open position due to the high temperature of the compartment 2s. The operation of the fan motor 43 and the compressor motor 125 will reduce the temperature of the evaporator 38 as Well as the temperatures of the compartments 22 and 26. This will gradually cause the throttling of the valve 58 and also will cause the movement of the projection 72 away from the plunger '74- to cause the double-throw switch 242 to move away from its upper contact 258 and back into contact with its lower contact 244. This restores the system to normal operation. Inasmuch as the heater 238 is compensated for voltage variations in the supply, the system is quite reliable and will provide defrosting only when required. High temperatures of the above-freezing compartment 26 are thus effectively prevented by the operation of the fan motor 43 and the compressor motor 125.

In the form shown in FIGURE 5, the defrosting system is the same as that shown in FIGURE 4 and bears the same reference characters and operates in a similar manner with similar advantages. The control system difi'ers from that in FIGURE 4 in that, when the temperature of the above-freezing compartment 26 and the temperature of the bulb 70 of the valve 58 rise to the abnormally high tem penature, only the fan 48 is placed in operation without causing the operation of the compressor motor 125. The first supply conductor 27!! connects directly with the switch 234 of the defrost thermostat 73. The second supply conductor 272 connects with the adjacent terminals of the deirost heater 169, the thermistor 254, the fan motor 48 and the compressor motor 125. It also connects with the conductor 259. The other terminal of the compressor motor connects through the conductors 274 and 276 with the thermostatic snap-action switch 131 connecting through the conductor 278 with the contact 232 of the defrost switch 78. The conductor 274 also connects with a conductor 236 connecting with the contact 282 of the valve operated switch 76.

The plunger 74 controls the movable double throw switch member 284 normally connecting the conductor 280 with the conductor 286 connecting with the adjacent terminal of the fan motor 48 so that normally the snap-acting switch 131 will simultaneously energize and deenergize the fan motor 43 and compressor motor 125. The conductors 288 and 290 connect with a contact 292 of the valve actuated switch'76 which normally connects through the single throw switch member 294 with the resistor 246 connecting with the defrost control heater 238 and the thermistor 254 of the automatic defrost system. The switch members 284 and 294 are connected together and to the plunger 74 for simultaneous snapaction operation. This circuit and control arrangement provides for normal operation of the refrigerating system.

However, should there be an abnormal rise in temperature of the above-freezing compartment, the valve 58 will move to a wide-open position in which the projection 72 engages the plunger 74 to move the switch member 284 into contact with the contact 296, thereby disconnecting the fan motor 48 from the control of the snap-acting switch 131 and connecting it through the conductors 298, 288, 278, the contact 232 and the snapacting bimetal switch 234 to the supply conductor 27%. This will cause the fan motor 48 to operate to increase the cooling provided for the above-freezing compartment 26. At the same time the switch member 294 will be moved away from the contact 292 to open position into engagement with a stop so that the heater 238 will be deenergized. This, however, will not immediately provide a defrost cycle unless the evaporator 38 is heavily frosted. Even this will not take place immediately but will require some time before the snap-acting bimetal switch 234 is cooled to its operating point of 28 F. This provides a way in which the above-freezing compartment 26 may be provided with additional cooling under high temperature conditions. This additional cooling by operating the fan motor 48 is of particular advantage even though a defrost cycle is to follow since this will cool the compartment prior to the defrost cycle and thereby premnt an excessive rise in the temperature of the above-freezing compartment 26 during the. defrost period.

. In the form shown in FIGURE 6, the defrost system is again the same as is shown in FIGURES 4 and and bears the same reference characters. then the above-freezing compartment 26 reaches an abnormally high temperature, the operation of the plunger 74 acts to deenergize the defrost control heater 238 and to energize a small element heater associated with the thermostat bulb 140 of the snap-action switch 131. In detail, the supply conductor 321 connects directly with the snapacting bimetal switch 234 of the defrost control switch 78. The second supply conductor 323 connects with the defrost heater 160, the conductor 250, the thermistor 254, the fan motor 48 and the compressor motor 125. The fan motor 48 and the compressor motor 125 are connected by the conductors 325, 327 and 329 to the snap-action switch 131 which in turn connects through the conductor 331 to the contact 232 and the bimetal snap-acting switch 234 with the supply conductor 321. When the above-freezing compartment 26 reaches an abnormally high temperature, the thermostat bulb 70 likewise will reach an abnormally high temperature thereby moving the valve 58 to its wide-open position in which the projection '72 will engage the plunger 74 of the switch 76. In this form, the switch 76 is provided with a double-throw snap-action switch member 333 normally in engagement with the contact 335.connecting with the circuit for the defrost control heater 238. The

switch 76 is of the snap-acting type and when the plunger 74 is engaged, the double-throw contact member 333 will be snapped away from the contact 335 into engagement with the opposite contact 337 connecting with the heater 339 which is associated with the thermostat bulb 140. The heater 339 heats the bulb 140 to increase the pressure in the fluid motor of the snap-acting thermostatic switch 131 to cause its closing ,to energize both the fan motor 48 and the compressor motor to provide refrigeration to the above-freezing compartment 26 to lower its temperature. The resultant loweringof the temperature of the compartment 26 and the bulb 70 will cause the valve 53 to release the plunger 74 to deenergize the heater 339. The defrosting system bears the same reference characters and operates similar to that of FIGURE 4.

Thus, in all the forms of the invention illustrated, the rise in temperature of the compartment 26 will operate the plunger 74 to cause operation of the fan motor to provide increased cooling for both compartments. In the forms of FEGURES 3, 4 and 6, the compressor motor 125 is also operated to further cool the evaporator 38.

While the embodiments of the present invention, as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A refrigerator including insulating means enclosing a below-freezing compartment and an above-freezing compartment and door means for access to said compartments, a refrigerating system comprising liquefying means and evaporating means for cooling said compartments, fan means for circulating air from said abovefreezing compartment and said below-"reeling compartmerit into heat transfer relation with said evaporating means and returning the air to said compartments, a thermostatic air valve responsive to the temperature of the air in the above-freezing compartment for throttling the air returned to said above-freezing compartment to maintain above-freezing temperatures therein, means responsive to a predetermined low temperature of said below-freezing compartment for normally stopping said liquefying means and said fan means, and means responsive to a predetermined opening of said air valve for starting said fan means.

2. A refrigerator according to claim 1 in which the means responsive to a predetermined low temperature of the below freezing compartment comprises a thermostatic switeh provided with a thermosensitive element provided with a low wattage electric heater thermally associated with it and in which the means responsive to a predetermined opening of said air valve comprises a switch for energizing said electric heater to influence the closing of said thermostatic switch.

3. A refrigerator including insulating means enclosing a below-freezing compartment and an above-freezing compartment and door means for access to said compartments, a refrigerating system comprising liquefying means and evaporating means for cooling said compartments, fan means for circulating air from said abovefreezing compartment and said below-freezing compartment into heat transfer relation with said evaporating means and returning the air to said compartments, a thermostatic air valve responsive to the temperature of the air in the above-freezing compartment for throttling the air returned to said above-freezing compartment to maintain above-freezing temperatures therein, means responsive to a predetermined low temperature of said below-freezing compartment for normally stopping said liquefying means and said fan means, and means responsive to a predetermined opening of said air valve for starting said fan means and said refrigerating system.

4. A refrigerator including insulating means enclosing a below-freezing compartment and an above-freezing compartment and door means for access to said compartments, a refrigerating system .comprising liquefying means and evaporating means for cooling said compartments, fan means for circulating air from said abovefreezing compartment into heat transfer relation with said evaporating means and back to the above-freezing compartment, said liquefying means and said fan means each being provided with separate electric driving motors,

a first thermostatic snap-acting switch responsive to the temperature of the below-freezing compartment and normally electrically connected in series circuit with both of said electric driving motors, and a second thermostatic switch and circuit means responsive to the temperature of said above-freezing compartment for connecting the electric driving motor of said fan in shunt with said first switch and said electric driving motor for said liquefying means.

5. A refrigerator including insulating means enclosing a below-freezing compartment and an above-freezing compartment and door means for access to said compartments, a refrigerating system comprising liquefying means and evaporating means for cooling said compartments, fan means for circulating air from said abovefreezing compartment into heat transfer relation with said evaporating means and back to the above-freezing compartment, defrosting means for defrosting said evaporating means, a snap-acting defrosting thermostatic control means responsive to a predetermined low temperature of said evaporating means for rendering effective said defrosting means, said defrosting control means having a thermosensitive element in contact with a portion of said evaporating means provided with a small Wattage element heater, said defrosting control means including means responsive to a predetermined high temperature of said evaporating means for terminating the operation of said defrosting means and for energizing said element heater and said refrigerating system and said fan means, means responsive to a predetermined low temperature of said below-freezing compartment for stopping said refrigerating system and said fan means, and means responsive to a predetermined high temperature of said above-freezing compartment for deenergizing said element heater and starting said fan means.

6. A refrigerator including insulating means enclosing a belovv-freezing compartment and an above-freezing compartment and door means for access to said c mpartments, a refrigerating system comprising liquefying means and evaporating means for cooling said compartments, fan means for circulating air from said abovefre-ezing compartment into heat transfer relation with said evaporating means and back to the above-freezing compartment, defrosting means for defrosting said evaporating means, a snap-acting defrosting thermostatic control means responsive to a predetermined low temperature of said evaporating means for rendering effective said defrosting means, said defrosting control means having a thermosensitive element in contact With a portion of said evaporating means provided with a small wattage elernent heater, said defrosting control means including means responsive to a predetermined high temperature of said evaporating means for terminating the operation of said defrosting means and for energizing said element heater and said refrigerating system and said fan means, means responsive to a predetermined low temperature of said below-freezing compartment for stopping said refrigerating system and said fan means, and means responsive to a predetermined high temperature of said above-freezing compartment for deenergizing said element heater and starting said fan means and said liquefying means.

References Cited by the Examiner UNITED STATES PATENTS 2,812,642 11/57 Jacobs 62180 2,907,180 10/59 Mann 62419 2,997,857 8/61 Clark 62419 3,110,158 11/63 Kuhn 62-419 ROBERT A. OLEARY, Primary Examiner. MEYER P'ERLIN, Examiner. 

1. A REFRIGERATOR INCLUDING INSULATING MEANS ENCLOSING A BELOW-FREEZING COMPARTMENT AND AN ABOVE-FREEING COMPARTMENT AND DOOR MEANS FOR ACCESS TO SAID COMPARTMENTS, A REFRIGERATING SYSTEM COMPRISING LIQUEFYING MEANS AND EVAPORTATING MEANS FOR COOLING SAID COMPARTMENTS, FAN MEANS FOR CIRCULATING AIR FROM SAID ABOVEFREEZING COMPARTMENT AND SAID BELOW-FREEZING COMPARTMENT INTO HEAT TRANSFER RELATION WITH SAID EVAPORATING MEANS AND RETURNING THE AIR TO SAID COMPARTMENTS, A THERMOSTATIC AIR VALVE RESPONSIVE TO THE TEMPERATURE OF 